Semiconductor devices used in a mobile communication tool such as cellular phone, smartphone, etc. are required to restrain unnecessary electromagnetic waves from leaking to the outside as much as possible, not to exert a negative influence on communication properties. Accordingly, a semiconductor package having an electromagnetic shielding function has been proposed.
For example, electromagnetic shielding of the semiconductor package is performed by covering the surface of a package made of resin with a metal film for electromagnetic shielding, to make this metal film electrically contact with the ground layer of a semiconductor chip in the semiconductor package.
The process of covering the surface of resin with a metal film can be performed by using a sputtering device used in a preceding step in the semiconductor manufacturing process. The sputtering device can simultaneously form uniform metal films for a plurality of semiconductor packages. Therefore, work efficiency can be improved if many semiconductor packages which completed a packaging process are placed on a carrier, conveyed to a sputtering device, and taken into a sputtering vacuum chamber together with the carrier to go through sputtering treatment.
However, the metal sputtered in the sputtering device adheres not only to the top and side surfaces of each semiconductor package but also to the surface of the carrier. Since the dirt on the carrier increases, the carrier must be cleaned frequently, which increases maintenance cost.